"Some U.S. officials pretend that they are mad. Of course I don't agree with that, but they are first-class idiots," he said in the speech in Tehran on January 9, according to his official Twitter feed.

Khamenei's comments were unusually crude, reflecting increasing tensions between Iran and Washington after President Donald Trump withdrew the United States from a landmark nuclear deal between Iran and world powers.

Khamenei also taunted an unnamed U.S. official for predicting there would be regime change in Iran by the end of 2018.

"A while ago, a U.S. politician had said, among a gathering of terrorists and thugs, that he hopes to celebrate this Christmas in Tehran," Khamenei said, according to his Twitter feed.

"Christmas was a few days ago. This is how U.S. calculations work."

It was unclear which U.S. official Khamenei was referring to, but members of the Trump administration have called for regime change and predicted it would happen soon.

This has included national-security adviser John Bolton who often speaks at gatherings of the exiled People's Mujahedeen of Iran (MEK) opposition group, considered a terrorist movement by Tehran's leaders.

"Before 2019 we here will celebrate in Tehran," Bolton told an MEK meeting in Paris in July 2017.

The United States reinstated sanctions on Iran in November after pulling out of a 2015 nuclear deal, in which Tehran received international sanctions relief in exchange for curbs on its nuclear program.

That move has exacerbated the country's economic problems, with Iran's currency, the rial, losing around half of its value against the U.S. dollar last year.

RFE/RL journalists report the news in 26 languages in 22 countries where a free press is banned by the government or not fully established. We provide what many people cannot get locally: uncensored news, responsible discussion, and open debate.